Updating set-type collections with multiple elements. Is it possible?

[Yi Zhou]

From the CQL documentation, all the examples incrementally update the set collections, one element at a time : http://docs.datastax.com/en/cql/3.1/cql/ddl/ddl_updating_collection_c.html

Is it possible to specify all the new values for your set collection in one query?

Previously I tried this prepared query :
"UPDATE social.events SET attending_userids = attending_userids + (?) WHERE event_id = (?);"

Attending_userids is set<bigint>
I tried binding a set<bigint> collection (CASS_COLLECTION_TYPE_SET) to the first (?) but I got the error : Error: Invalid tuple type literal for attending_userids of type set<bigint>

Is there a problem with my prepared query, or the multi-item set insert is not possible with cql?
If we can insert only one item at a time, does that mean instead of binding set<bigint> I need to SET attending_userids = attending_userids + {(?)} , where (?) is binded by bigint?

Thanks.

[Michael Penick]

Unfortunately, I don't this this is supported by the CQL syntax. When I try:

1)

Query:

"UPDATE examples.test_set SET value = value + {?} WHERE key = ?" 

Result: 

"Invalid set literal for value: bind variables are not supported inside collection literals"

2)

Query: 

"UPDATE examples.test_set SET value = value + ? WHERE key = ?"

Result: 

"Expected 4 or 0 byte int (16)"

I think you need to dynamically build a query with the correct number of "?" in the set/map literal. For example, a two items update would need to have a set of two items: "UPDATE examples.test_set SET value = value + {?, ?} WHERE key = ?", then use multiple calls to "cass_statement_bind_*()".

Mike

PS:

Here's my the code I used to try this:

#include <stdio.h>

#include <cassandra.h>

/* Schema:

 * CREATE KEYSPACE examples WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 2 };

 * CREATE TABLE test_set(key int PRIMARY KEY, value set<text>);

 *

 * Precondition:

 * INSERT INTO test_set (key, value) VALUES (1, {'item1', 'item2'});

 */

int main() {

  /* Setup and connect to cluster */

  CassCluster* cluster = cass_cluster_new();

  CassSession* session = cass_session_new();

  /* Add contact points */

  cass_cluster_set_contact_points(cluster, "127.0.0.1,127.0.0.2,127.0.0.3");

  CassFuture* connect_future = cass_session_connect(session, cluster);

  if (cass_future_error_code(connect_future) == CASS_OK) {

    /* These don't work */

    /*CassString query = cass_string_init("UPDATE examples.test_set SET value = value + {?} WHERE key = ?");*/

    CassString query = cass_string_init("UPDATE examples.test_set SET value = value + ? WHERE key = ?");

    CassStatement* statement = cass_statement_new(query, 2);

    CassCollection* coll = cass_collection_new(CASS_COLLECTION_TYPE_SET, 2);

    cass_statement_bind_int32(statement, 0, 1);

    cass_collection_append_string(coll, cass_string_init("item3"));

    cass_collection_append_string(coll, cass_string_init("item4"));

    cass_statement_bind_collection(statement, 1, coll);

    cass_collection_free(coll);

    CassFuture* future = cass_session_execute(session, statement);

    if (cass_future_error_code(future) == CASS_OK) {

      printf("Success!\n");

    } else {

      CassString message = cass_future_error_message(future);

      fprintf(stderr, "Error running query: %.*s\n", (int)message.length, message.data);

    }

    cass_statement_free(statement);

  } else {

    CassString message = cass_future_error_message(connect_future);

    fprintf(stderr, "Error connectin: %.*s\n", (int)message.length, message.data);

  }

  cass_future_free(connect_future);

  cass_session_free(session);

  cass_cluster_free(cluster);

  return 0;

}

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